Comparative study of the generic and chromosomal variation using RAPD marker method

Brachyscome Cass由大约80个物种组成，分布在从降雨区到澳大利亚干旱地区的各种栖息地。该属表现出非凡的染色体多功能性，包括结构变化和从n=2到15的数量变化以及种内多倍体，因此为从基因或其他DNA分子的结构变化来研究染色体进化提供了极好的机会。采用聚合酶链反应方法，对染色体数目不同但亲缘关系较近的物种间的属性差异进行了分析。在RAPD标记分析中，我们没有检测到物种特有的条带模式。当n=9时，类群的频带分布较为保守，而当n=3和4时，即使在同一种内，其频带分布也存在显著差异。在adh基因多态性分析中，n=9的种有一个信号PCR产物。而n=3和4的分类群有3个或更多的PCR产物含有内含子序列中的插入元素。有趣的是，与染色体数较高的物种相比，n=9的物种在染色体和分子水平上都是保守的。在染色体数量较少的高级一年生物种中，基因组重组不仅发生在染色体水平上，而且发生在分子水平上。

Brachyscome Cass comprises about 80 species and occurs in a diversity of habitats from the rainfall zones to the arid regions of Australia. This genus shows extraordinary chromosomal versatility, involving structural changes and variation in number from n=2 to 15 as well as intraspecific polyploidy and thus offers excellent opportunities to examine chromosomal evolution from the structural changes in genes or other DNA molecules. We analyzed generic differences among species which have different chromosome numbers, n=9,4,3, but closely related each other, using polymerase chain reaction method.1. In the RAPD marker analyzes, we could not detected species specific band patterns. Band patterns of the taxa having n=9 were conservative, while those with n=3 and 4 showed significant variation even within the same species.2. In the analyzes of the adh gene polymorphism, species with n=9 had a signal PCR products. While taxa with n=3 and 4 had three or more PCR products which contained inserted elements in the intron sequence.It is interesting that the species with n=9 are conservative both chromosomal and molecular levels in comparison with those of species with the advanced chromosome number. Genomic reorganization has occurred not only at the chromosomal levels but also at the molecular ones in the advanced annual species with small chromosome number.